On 22-09-2022 13:38, Dr. Arne Babenhauserheide wrote:
> 
> Tobias Geerinckx-Rice <me@tobias.gr> writes:
> 
>>> can I express "any version of ffmpeg"?
>>
>> No, this would go against the goals of Guix: packages can't depend on properties of the environment they'll end up in (if any).
> 
> What’s the right way to deal with this, then? I need ffmpeg at as
> propagated-input, but I do not want to create a conflict with a manifest
> that just defines "ffmpeg".

In one my replies, I have proposed a method that avoids propagating ffmpeg:

> To avoid profile collisions when the user installed a different version of ffmpeg (e.g. ffmpeg@5) in their profile, could you modify the code to look at a /gnu/store/.../bin/ffmpeg instead?  Likewise for bubblewrap, gdk-pixbuf, poppler and librsvg, if feasible.
> 
> For ffmpeg, the following function needs to be modified:
> 
> https://0xacab.org/jvoisin/mat2/-/blob/master/libmat2/video.py#L139
> 
> (substitute* + search-input-file can be useful). 

Greetings,
Maxime.